Dynamic Analysis Of A Dual Rotor System By Component Mode Synthesis

The dual-rotor system is widely used as a main structure of aero-engine, and its dynamic characteristics have great influence on the capability of aero-engine. Therefore, in order to further improve the capability of aero-engine and promote the development of aero-industry in our country, it is very necessary to study the dynamic characteristics of the dual-rotor system.In view of the structural features of the dual-rotor system, the dynamic model is established. The equations of motion are established based on the theory of rotor dynamics. Then the fixed interface method for component mode synthesis is applied to the dual-rotor system. The system is divided into two substructures whose gyroscope modes are calculated. For each substructure, the first eight pairs of gyroscope modes and constraint modes are assembled to form the modal matrix, by which the equations of motion are transformed from physical coordinates to modal coordinates. The equations of the system after component mode synthesis are acquired by way of equations coupling of two substructures through the supporting force of rolling bearing. Compared with the 80-dimensional equation in state space, the equation after component mode synthesis is a 40-dimensional one, so the scale of computation is decreased.With the help of MATLAB, numerical computation is conducted on unbalance response of the dual-rotor system below three kinds of working speed including low, middle and high speed. It is proved that using of component mode synthesis not only ensures computation accuracy, but also enhances computation efficiency and saves computation time. Then the relationship between the amplitude of steady-state response and the speed of rotor is simulated for different kinds of procession. It is indicated that the results of component mode synthesis are almost consistent with the results of the original system, and only small errors exist in the neighborhood of the third resonance speed area. Finally, three-dimensional waterfall plots of steady-state response and critical speeds are obtained by using of component mode synthesis.